Yeah, love my Steam Deck - I thought I would mostly use it for work (ie: companion for night shift) but I find I'm logging onto it at home frequently.
The types of games I mainly play on it are games that are suitable for a small screen, ie: retro-inspired titles, 2D titles, JRPGs, turn based strategy games, etc. I tried to play Horizon Zero Dawn on it - and it plays it smoothly enough, but at 30fps, which doesn't feel good to me. It plays Tales of Arise easily enough at 40fps, which feels alot more playable. Still I view this as primarily a handheld system, and keep my 'heavier' titles for my desktop PC.
I haven't ran into too many games from my library that didn't run on Steam Deck, the games that weren't playing 'out of the box' usually ran well enough with an experimental branch of Proton. I haven't played around much with emulators, but I have accessed my Epic and GOG libraries through the Hero Launcher (nowhere near as smooth a process as native Steam titles, but easy enough to get running.)
But my favourite feature of the Steam Deck is the 'suspend/resume' feature. It's been a common feature with consoles for a couple of generations now and is something I always wanted for PC, but never had it until the Deck. I love that feature so much, that if Valve ever makes Steam OS 3 officially available for DIY PC builders, I'd build a dedicated gaming rig solely for Steam OS and that feature. I'd then have my primary PC either a lightweight laptop or a tiny ITX build focused solely on non-gaming tasks.